It is desirable to decrease the malfunction rate of firearms, for example, bolt action rifles fed ammunition from rotary magazines. Some malfunctions find their cause in the characteristics of the magazine. For example, some prior art magazines suffer weak cartridge stack recovery. Weak cartridge stack recovery can cause bolt overrides, concomitant failure to feed, as well as permit excessive inertial movement of cartridges during recoil impulse. Weak cartridge stack recovery is attributable to a number of factors including cumulative friction between cartridges and high contact stress between cartridges due to single point contact between cartridges when subjected to force from a spring-biased follower. Unfavorable reaction force vectors between the follower paddle and the contacting cartridge (particularly in the fully loaded condition) are believed to be a particularly pernicious source of problems, as shown in FIG. 1 and described below.
An example prior art magazine 11 is shown in FIG. 1. Tests indicate that sources of firearm malfunction include the top cartridge 13a not being biased by the follower 15 sufficiently against the magazine lips 17, thereby allowing the cartridge to be forced back down into the magazine in response to inertial forces when subjected to recoil impulse. Some cartridges become trapped within the magazine as a result and are prevented from engaging the feed lips. Trapped cartridges are out of position for feeding upon cycling of the bolt and may cause a malfunction. Another malfunction is caused by the base or head of the top cartridge 13a slipping down the follower 15 away from the magazine lips 17. Even relatively small slippage may allow the bolt to override the top cartridge and not feed properly. These malfunctions are believed rooted in large part in the engagement between the follower and the last cartridge 13b, where it is observed that the force vector 19 between the follower 15 and the last cartridge 13b is normal to the contacting surface of the follower and thus not in the most advantageous direction to urge the cartridges into engagement with the magazine lips 17. This disadvantageous orientation of the contact vector is believed due to the fact that the prior art follower is flat along the length of the cartridge and thus does not account for the orientation of the last cartridge 13b due to the cartridge's tapered shape, or the change in cartridge angle relative to the follower as cartridges are removed from the magazine. There is an opportunity to improve the reliability of firearms, particularly bolt action rifles, by improving the characteristics of the ammunition magazine.